Ab-initio molecular dynamics simulation of monolayer C 60 thin film on silicon (100) surface

Two dimensional band structure is calculated for a triangular lattice of C60 molecules by using a mixed-basis approach in which wave functions are expanded with not only plane waves but also 1s and 2p atomic orbitals of carbon atoms. The present analysis modeling a charge transfer from Si dimers of the Si (100) surface suggests the existence of a small Fermi-surface. The resulting partial charge distribution is consistent with the recent STM observation of specific stripes, the direction of which is parallel to that of the topmost double bond of C60, regardless of the intermolecular interaction. It is concluded that the orientation of C60 on the Si surface is mainly determined by the direction of dimer arrays and not by the interaction between C60 molecules.